The subject matter disclosed herein relates generally to antenna arrays, and more particularly to a dual-frequency coil array for a Magnetic Resonance Imaging (MRI) system.
MRI systems include a magnet, such as a superconducting magnet that generates a temporally constant (i.e., uniform and static) primary or main magnetic field. MRI data acquisition is accomplished by exciting magnetic moments within the primary magnetic field using magnetic gradient coils. For example, in order to image a region of interest, the magnetic gradient coils are energized to impose a magnetic gradient to the primary magnetic field. Transmit radio-frequency (RF) coils are then pulsed to create RF magnetic field pulses in a bore of an MRI scanner to selectively excite a volume corresponding to the region of interest in order to acquire MR images of the region of interest using receive RF coils. The resultant image that is generated shows the structure and function of the region of interest.
In these MRI systems, the RF coils (essentially near field antennas) are current loops that are tuned to resonate at a desired Larmor frequency for particular nuclear species. While most MRI scanners operate primarily at the frequency of the common hydrogen nucleus, other frequencies are possible, for the observation of other nuclei, such as 13C, the magnetic nuclide of carbon. For dual (or multi) frequency MRI systems, doubly (or double) resonant tuning of the antennas is often needed to facilitate operation at both frequencies in a single exam. This doubly resonant tuning may be provided with the dual resonance of a single RF coil or with two separate coils each individually tuned and that typically include geometric and/or circuit-trap decoupling. Electromagnetic decoupling of individual RF coil elements is needed to minimize crosstalk between channels of the MRI system.